ANSWERS

1. List the functions of the lymphatic system.
   • The return of excessive tissue fluid to the circulation.
   • Filtration of bacteria and foreign material from the fluid within the lymph nodes.
   • The production of lymphocytes.
   • The transportation of digested food (particularly fat).
2. What are lymphocytes?
   White blood cells formed in the lymph tissue whose function is the production of immune bodies that protect the body against infection.
3. What is lymph?
   Lymph is the fluid from the blood that has transuded through capillary walls to supply nutriment to tissue cells. It is collected by lymph vessels which ultimately return it to the blood.
4. List the 4 main components of the lymphatic system, and briefly describe the function of each.
   • Lymphatic capillaries - fine channels that collect surplus tissue fluid; join together to form lymphatic vessels.
   • Lymphatic vessels - thin-walled structures that transport the lymph via non-return valves.
   • Lymphatic tissues - specialised tissues responsible for the filtration of bacteria and foreign material from the lymph aswell as the production of antibodies.
   • Lymphatic ducts - these are responsible for draining the lymph into the right jugalar vein or anterior vena cava (there are 2; the right drains the right forelimb and right side of the head and neck, whilst the left drains the rest of the body).
5. What are the lymphatic capillaries found within the villi of the small intestine called?
   Lacteals.
6. State the 2 functions of lymph nodes.
   • Filtration of bacteria and foreign material from the lymph.
   • Production of lymphocytes.
7. What is a portal, and why is this relevant to this module?
   A portal of the body is an area where inside meets outside; lymph nodes are found at the tops of limbs but also at portals including those found in the pharynx, mediastinum and within the mesentery of the small intestine.
8. List the 10 lymph nodes, and state the location of each.
   • Parotid - there are 2 parotid glands, one in front of each ear.
   • Retropharyngeal - behind the pharynx.
   • Submandibular - beneath the mandible (lower jaw bone).
   • Prescapular - in front of the shoulder-blade.
   • Axillary - within the "arm-pit" .
   • Bronchial - within the thorax (chest).
   • Cisterna chyli - within the intestine.
   • Mesenteric - within the intestine.
   • Superficial inguinal- within the groin.
   • Popliteal - within the stifle (knee joint of the hind limb).
9. What do the cisterna chyli and thoracic duct have in common?
   They are both part of the left lymphatic duct. The cisterna chyli is the abdominal part of the duct, whilst the thoracic duct is so called once it has crossed the diaphragm into the thorax.
10. List 4 structures that contain lymphatic tissue.
    • Lymph nodes.
    • Tonsils.
    • Thymus.
    • Spleen.
11. List the 4 main functions of the spleen.
    • Storage of red blood cells.
    • Destruction of worn-out red blood cells.
    • Production of lymphocytes.
    • Filtration of bacteria and other foreign matter from the circulation by phagocytosis.
12. What might enlarged lymph nodes indicate?
    Local infection or invasion by tumour cells.